Real GTS or not.

Vin# on the Rad support punched into the metal off center closer to the driver side of car generally. The same number punched on the weather seal lip of the trunk drip rail under the weather strip and can be hard to see. It can be easier to see/read from inside the trunk looking up at the lip. As well, Check the leaf springs one extra on the pass side and you may even find a P# on them, yes they could have also been swapped out but just another place to confirm. Check torsion bar #'s 340 bars have a unique number over 6-273,318 ETC. These are just a few hints....the more hints the clues add up :) Good luck searching!